There was a silver lining in what has been dubbed the “world’s biggest ransomware attack” – it struck on Friday mid-afternoon (in Europe), just as businesses were winding down for the weekend, and as a result the full impact of the forced system shutdowns would not be fully felt over the weekend when businesses and infrastructure are generally operating at a subdued pace. However, with the weekend coming to a close, the full extent of the inflicted damage may become apparent in just a few hours.

That was the warning by Europol Executive Director Rob Wainwright who on ITV’s “Peston on Sunday” broadcast, said that additional disruptions are likely as people return to work Monday and turn on their desktop systems, and as a result the “unrivaled” global cyberattack is poised to continue claiming victims.

Speaking to ITV’s, Wainwright added the attack was indiscriminate across the private and public sectors.

“At the moment we are in the face of an escalating threat, the numbers are going up, I am worried about how the numbers will continue to grow when people go to work and turn their machines on Monday morning.”

“The latest count is over 200,000 victims in at least 150 countries. Many of those will be businesses including large corporations.

“We’ve seen the rise of ransomware becoming the principal threat, I think, but this is something we haven’t seen before — the global reach is unprecedented,” Wainwright also said. He also said that organisations across the globe, including investigators from the National Crime Agency (NCA), are now working non-stop to hunt down those responsible for the ransomware.

As we reported on Saturday, the initial attack was halted when a security researcher disabled a key mechanism used by the worm to spread, but experts said the hackers were likely to mount a second attack because so many users of personal computers with Microsoft operating systems couldn’t or didn’t download a security patch released in March that Microsoft had labeled “critical.” Microsoft said in a blog post Saturday that it was taking the “highly unusual“ step of providing the patch for older versions of Windows it was otherwise no longer supporting, including Windows XP and Windows Server 2003.

As the WSJ confirms, the attacks could worsen on Monday morning because of how the virus works.

The virus contains two parts. One is the ransomware, which locks the computer files and displays a message saying that the files will be locked and eventually destroyed unless the user sends payment over the internet to the hacker.

The other part is known as the “spreader.” Once the virus makes its way onto one computer–perhaps when a user opens an infected email attachment–the spreader transmits itself to other computers on the network.

The British researcher, who wishes to be identified only as MalwareTech, found a kill switch in the spreader. The spreader was designed to contact a web address to see whether it should further spread itself, but hackers hadn’t bought that web address. So MalwareTech did, and effectively stopped the virus’s spread. It meant that one computer in a network could be infected, but the worm wouldn’t spread to the rest of the network.

Cybersecurity experts expect the latest versions of the worm to have no kill switch for the spreader. So when workers return to the office Monday morning and turn on their computers, they might open an infected email attachment or connect an already-infected laptop to their organization’s non-security-patched network and spread the worm.

There was some good news: having tipped their hand on Friday, and allowing hacking countermeasures to be implemented, about 97% of U.K. facilities and doctors disabled by the attack were back to normal operation, Home Secretary Amber Rudd said Saturday after a government meeting. As reported on Friday, at the height of the attack Friday and early Saturday, 48 organizations in the NHS were affected, and hospitals in London, North West England and Central England urged people with non-emergency conditions to stay away as technicians tried to stop the spread of the malicious software.

“There will be lessons to learn from what appears to be the biggest criminal cyber-attack in history,” Rudd said cited by Bloomberg in response to a letter from Jonathan Ashworth, the shadow secretary of state for health.

Meanwhile, according to Tom Robinson, chief operating officer and co-founder of Elliptic Enterprises Ltd., a ransomware consultant that works with banks and companies, victims have already paid about $30,000 in ransom so far, with the total expected to rise substantially next week, said . Robinson, in an interview by email, said he calculated the total based on payments tracked to Bitcoin addresses specified in the ransom demands. The number, which is likely a conservative estimate, will only embolden the hackers to become even more aggressive in their next attack.

Ransomware is a particularly stubborn problem because victims are often tricked into allowing the malicious software to run on their computers, and the encryption happens too fast for security software to catch it. Some security expects calculate that ransomware may bring in as much as $1 billion a year in revenue for the attackers.

According to Bloomberg, last year an acute-care hospital in Hollywood paid $17,000 in bitcoin to an extortionist who hijacked its computer systems and forced doctors and staff to revert to pen and paper for record-keeping.

On one hand, it is probable that the weekend gave many companies the opportunity to prepare for the next ransomware attack: “While any sized company could be vulnerable, many large organizations with robust security departments would have prioritized the update that Microsoft released in March and wouldn’t be vulnerable to Friday’s attack.”

Even so, it does not explain why some of the world’s biggest corporations were so strikingly unprepared for Friday’s events.

A spokesman for Spain’s Telefonica SA said the hack affected some employees at its headquarters, but the phone company is attacked frequently and the impact of Friday’s incident wasn’t major. FedEx said it was “experiencing interference,” the Associated Press reported.

Renault halted production at some factories to stop the virus from spreading, a spokesman said Saturday, while Nissan’s U.K. car plant in Sunderland, in northeast England, was affected without causing any major impact on business, an official said.

In Germany, Deutsche Bahn faced “technical disruptions” on electronic displays at train stations, but travel was unaffected, the company said in a statement on its website. Newspaper reports showed images of a ransomware message on display screens blocking train information.

Russia’s Interior Ministry, with oversight of the police forces, said about “1,000 computers were infected,” which it described as less than 1 percent of the total, according to its website.

Indonesia’s government reported two hospitals in Jakarta were affected.

Meanwhile, the latest anti-Russia narrative is growing.

“There is a high probability that Russian-language cybercriminals were behind the attack” said Aleks Gostev, chief cybersecurity expert for Kaspersky Labs. “Ransomware is traditionally their topic,” he said. “The geography of attacks that hit post-Soviet Union most also suggests that.” In retrospect, what more convenient confluence of events could there be than having a handy justification for Q2 GDP missing again – just blame it on the computer virus – and accusing Russia of being responsible for the latest global slowdown.